Mills Physics Professor Sheds Light on Soundscape of Electric Guitar Amplifiers

Oakland, CA—February 13, 2017

guitar and amplifierIn a new scholarly paper published this week in the journal Physics Education, Mills College Physics Professor David Keeports explains why rock music guitar riffs sound better through old-school vacuum tube amplifiers as opposed to the relatively newer transistor models.

Bay Area guitar legend Carlos Santana and guitarists in the band AC/DC are two examples of musicians who play through tube amplifiers, Keeports said.

The paper in Physics Education breaks down what rock guitarists have known for years, but may not have known why: that tube—or valve amplifiers as they are known as in England—produce stronger, more even harmonics and distortion than their transistor-run counterparts, which can create harmonics that “cause dissonance.”

Professor Keeports explores the physics of why even harmonics enrich a sound, and why the timbre of the sound from a tube amp changes when a guitar is played loud. The findings in his paper were also featured in the publication techradar.

“The even harmonics of a tube amp provide a complex, warm, rich sound that so many guitarists desire,” Keeports said. “Odd harmonics are pleasing to the ear, but not as much as even harmonics, and that is the reason for the preference of tube amps over transistor amps.”

Keeports has been teaching physics and chemistry at Mills since 1982. His professional interests include molecular spectroscopy, physics and chemistry education, and software development. A musician himself, whose father owned a television and radio store, Keeports said he owns “a lot of equipment” and is naturally curious about how and why it all works.